This invention relates to methods of uniform color fading, fading with patterns and marking patterns onto textiles materials, such as denim, using lasers. More particularly, it relates to using lasers to simulate conventional laundering techniques, such as stone washing, echo ball washing and acid washing without the use of water or chemicals. Still more particularly, it relates to performing the above mentioned process in an environmentally safe manner.
It is known that laser beams are used to record patterns in various materials. The great heat available when the laser beam is focused to a small spot can be used to change the physical properties of a material. In previous methods, the visible change in the material properties are produced by burning, charring, melting or other severe modifications of the physical characteristics of the material.
The present invention describes a method where intense laser radiation is directed onto a pre-dyed textile material such as denim. The laser parameters such as wavelength, average power, pulse duration, power density, and scan speed are adjusted to provide efficient absorption into the dye components of the textile material. The absorption of the laser radiation by the dye components results in rapid and selective photo-decomposition of the dye elements. The result of controlled exposure is a color fading or color removal effect.
Vapors and debris resulting from the rapid photo-decomposition of the dye elements in the textile material can be easily removed from the work environment by standard suction and filtration machinery now used in many industrial applications. In the industrial environment, this method is best applied on a moving web of textile material. In the case of broad coverage, the laser beam is scanned across the material in a direction perpendicular to the direction of the textile. The laser beam scan rate, power density, average power, pulse width, and repetition rate are synchronized to the speed of the textile material such that the desired fading pattern is created.
Currently, fading of textile materials, such as denim, is accomplished on finished clothing articles by a multi-stage laundering process that utilizes conventional washing machines, large quantities of water, and various chemical and mechanical additives that act on the fabric to produce the desired fading effects. Stone wash methods use actual stones or rocks in the washing process. These stones impact the denim material and result in the desired fading pattern. A variation of this method uses golf balls in place of stones in the washing process. This "Echo Ball" washing technique results in a similar pattern to that of stone watching. Another method of fading finished denim clothing is with the use of chemicals in an aqueous mixture containing alkaline or chlorine that causes a uniform fading of the colored textile material. More recent developments have included using enzymes or other bacteriological agents in the fading process.
Large amounts of water are used in the previous stone washing, echo ball washing, and acid washing fading methods. As much as 15 gallons of water is used per clothing article in these processes. At current annual production rates, the textile industry uses six billion gallons of water per year in the U.S. for denim finishing operations. Moreover, the water used in these processes is contaminated with dyes and other chemicals and often requires purification before being discharged. When purification is not required by law, the contaminated waste water is discharged into the environment.
All previous methods perform the fading process on textile materials that have been cut and sewn to form completed clothing article. This is the most practical method available today since conventional finishing methods are performed in industrial washing machines. Significant improvements could be realized in the manufacturing process if a method could be found to perform the fading operation on the material prior to it being cut and sewn into finished garment form.
Fading denim material after it is cut and sewn into finished garments adds time, labor, resources and costs to the finishing process. Thus, a need exists for uniformly fading and fading with patterns textile materials such as denim without the use of water or harsh chemicals. A need also exists for a method of fading and marking textile materials prior to assembly into finished garments.
Currently, marking detailed patterns on colored textile fabric, such as denim, is accomplished by methods similar to laser printers where dye is made to adhere to specific areas of a drum mechanism exposed to laser radiation. The drum with dye components is rolled across wet textile material to transfer the pattern. Other methods include applying heat to a film placed on the fabric.
Still other methods include the use of laser radiation to heat the textile to allow for better adhesion by the dyes. The prior patented art includes some methods for using a laser to mark various items, including textiles, but most require the use of wet dye solutions and none is like the present invention.
U.S. Pat. No. 4,861,620 by Azuma, et al., issued Aug. 29, 1989, describes a method of laser marking which requires that a pigment coating be placed on the surface of the article being marked. Then a focused laser beam is used to affect the internal molecular structure of the pigment to change color. U.S. Pat. No. 4,901,089 by Bricot, issued Feb. 13, 1990, discloses a method and device for the recording of pictures by laser which requires several layers of material be placed on a substrate. A laser beam is used to ablate the top material to form an image. U.S. Pat. No. 4,847,184 by Taniguchi, et al., issued Jul. 11, 1989, teaches a method for transferring a still video image onto a substrate that is carbonizeable or discolorable. Unlike the present invention, this technique engraves a pattern into the substrate to form a pattern of some depth. U.S. Pat. No. 5,017,423 by Bossmann, et at., issued May 21, 1991, teaches a process for manufacturing textile materials using lasers. In this method, a laser beam is used to cause a physical change in the textile material. This change, due to charring and burning effects, results in a larger cross-sectional area being exposed to the dyeing process. The larger cross section of the textile results in better dye adhesiveness. U.S. Pat. No. 5,248,878 by Ihara, issued Sep. 28, 1993, concerns marking golf balls using lasers. Finally, German Patent No. 39 16 126, involves using a laser beam to print a pattern on textile fabrics that is wet with dye. This latter method creates a pattern on the material by changing the color of the dye. Thus, a need exists for a method for marking various detailed patterns on colored textile fabrics without damaging the fabrics.
Unlike the above patents, the present invention uses an environmentally safe method for marking, fading and treating textile fabrics with a laser without the need for conventional washing methods, wet dyes, or excessive amounts of water.